1. Field of the Invention
The present invention pertains to apparatus for insertion in a wellbore and a method associated therewith for removal of solids accumulations in and around a gravel pack screen and other areas where solids may collect and interfere with the production of well fluids.
2. Background
In fluid producing wells and mineral leaching operations, for example, various types of solid particles and sediments tend to accumulate in the wellbores at various locations. It is generally desireable to prevent the accumulation of solids or sediments in order to avoid the restriction to the flow of produced fluids which is caused by such materials. It is often necessary in oil and gas wells, for example, to perform cleanout operations to remove accumulations of solids in the wellbores in the vicinity of the fluid producing formation. Such solids tend to accumulate in the rathole portion of the wellbore, in and around gravel pack screens or liners, and in other areas of the wellbore, such as on the transverse shoulders or other portions of mechanisms comprising parts of liner hanger structures, packers and other wellbore devices.
Conventional well cleanout operations involve the insertion of a relatively small diameter tubing string generally concentrically through the production fluid tube or conduit and into the wellbore below the end of the production tube in an effort to remove any accumulations of solids by pumping a fluid through the small tube to generate enough turbulence and fluid flow velocity such that solids are hopefully entrained with the jetted fluid and carried upward through an annular flow passage formed between the production fluid tubing and the circulating fluid tube.
However, conventional arrangements of production fluid tubing and cleanout fluid injection apparatus fail to provide for efficient and complete removal of a major portion of the solids from the wellbore, particularly solids which tend to accumulate on transverse surfaces formed by various in-the-well devices. Conventional arrangements of well cleanout systems therefore usually do not provide for the complete cleanout of solids and these solids tend to fall back into the gravel pack screen or liner, thereby blocking a portion of the liner structure from permitting the flow of production fluids. Incomplete cleanout of solids or sediments also introduces the possibility of accumulation of sufficient amounts of solids in the wellbore such as to prevent insertion of cleanout or injection tubing, particularly if there is otherwise a stoppage of fluid circulation or a reduction in the circulation rate in the wellbore.
Accordingly, there has been an acute need for an improved arrangement and method of cleaning out wellbores to remove accumulated solids, particularly in wellbores which include an otherwise conventional arrangement of a gravel pack liner or screen disposed in the wellbore below the open end of a production fluid tube or the like. It is to this end that the present invention is directed wherein there is provided an improved arrangement of a well cleanout system and an improved method of performing well cleanout or solids removal operations without removal of a portion of the well structure and wherein a more complete and thorough removal of accumulated solids is accomplished.